Diasynurella dzhamirzoevi Palatov et Marin, 2023

Palatov, Dmitry M. & Marin, Ivan N., 2023, Diversity of the Caucasian genus Diasynurella Behning, 1940 (Amphipoda: Crangonyctidae) with description of four new species, Arthropoda Selecta 32 (1), pp. 23-55 : 32-40

Diasynurella dzhamirzoevi Palatov et Marin sp.n.

Figs 6–11 .

MATERIAL EXAMINED. Holotype $ (bl. 4.0 mm), ZMMU Mb-1250, Russian Federation, Samur-Divichi lowland, Dagestan, Magaramkent district, Samur forest , about –1 m a.s.l., 41°50′35.5″N, 48°33′31.2″E, in small forest spring, hand net sampling, 31 December 2021, coll. D. Palatov. Paratypes 2$$ (bl. 4.0 mm), ZMMU Mb-1251, same locality and data as for holotype .

Additional material: 2$$, LEMMI, same locality and data as for holotype .

ETYMOLOGY. The species is named after the famous Dagestan scientist Dr. Gadzhibek S. Dzhamirzoev (“Dagestansky” State Natural Reserve).

DESCRIPTION. Female. Body ( Fig. 6 ): moderately stout; largest collected $ has bl. 4.5 mm. Head with wide rounded and little concave or straight anteroventral lobe ( Figs 7 a , 11 d ).

Antenna I ( Fig. 7 a ) about 55% of body length, about 2.0X longer than antenna II; primary flagellum with thirteen segments, with aesthetascs on distal segments; accessory flagellum 2-segmented, distal segment about 3.0X shorter than basal one ( Fig. 7 b ).

Antenna II ( Fig. 7 c ): gland clone distinct, distally pointed; peduncle about 2.0–2.3X longer than flagellum, with robust setae tightly covering segments III and IV; peduncle of segment IV about 1.1–1.2X longer than segment V; flagellum 6-segmented.

Mandible ( Fig. 8 c–f ): left mandible ( Fig. 8 c, d ) incisor 5-dentate, lacinia mobilis 5-dentate, with three robust plumose accessory setae; molar process with single seta. Right mandible ( Fig. 8 e, f ) incisor 4-dentate, lacinia mobilis toothed, triturative, lobes with numerous protuberances; underlying with row of three robust plumose setae; molar process similar to left mandible. Palp 3-segmented, segment II with six–seven setae; segment III about 3.2–3.5X longer than wide, with seven–eight separate D-setae, single B-seta and four separate E-setae ( Fig. 8 c, e ).

Labrum (upper lip) ( Fig. 8 a ): oval, apical margin with numerous small fine setae.

Labium (lower lip) ( Fig. 8 b ): inner lobes feebly developed.

Lateralia with 8 strong pectinate setae.

Maxilla I ( Fig. 8 g ): inner plate with two plumose marginal setae, outer plate with seven apical comb-spines; palp 2-segmented, distal segment pubescent, about 3X of basal segment, apical margin of distal segment with nine simple setae.

Maxilla II ( Fig. 8 h ): inner and outer plates covered in pubescent setae, subequal in length; outer plate weakly narrowing distally, with eleven apical setae; inner plate narrowing explicitly distally, with group of dense short setae on apex, with oblique row of short plumose setae.

Maxilliped ( Fig. 8 i ): inner plate much shorter than outer plate, with four spines and single simple seta apically, and 2–3 simple setae laterally; outer plate narrow, with row of 15–16 medial stiff simple setae of different length; palp quadriarticulate, article I with two simple setae on inner margin, article II with row of 16–18 simple setae on inner margin and without setae on outer margin, article III sub-quadrate; dactylus with single seta on outer margin and without setae at inner margin, nail long, slender, with one– two thin setae at hinge.

Gnathopod I ( Fig. 7 d, e ): smaller than GnII; coxal plate subtrapezoidal or suboval, slightly narrowing distally, with rounded corners and with three apical and numerous facial setae, width/depth ratio 0.67–0.69/1; basis width/length ratio is 0.31/1, with single long and two short setae on anterior margin, two long setae on inner face and four long setae on posterior margin; merus with 10–11 distal setae; carpus is 0.55X of basis and 0.80X of propodus in length, with ten serrated setae in inner margin and three simple setae in outer margin; propodus 1.86X longer than broad, with four simple setae in anterior margin and seven serrated single setae in posterior margin; distal margin of palm ( Fig. 7 e ) distinctly or slightly oblique, with double row of four inner and three outer robust setae; palmar groove (depression) feebly developed, with four inner and three outer robust setae; dactylus with single outer seta.

Gnathopod II ( Fig. 7 f, g ): coxal plate subovate, with three apical and numerous facial setae, width/depth ratios is 0.6/1; basis width/length ratio is 0.27/1, with several (three– four) long setae inserted along posterior margin and with two short simple setae in anterior margin; ischium with single short simple seta; merus with three–four distal setae; carpus is 0.62X of length of basis and 0.70X of propodus, with two anterior simple setae and four groups of plumose posterior setae; propodus 2.8X longer than broad, with single simple anterior seta, three–four superior medial, four inferior medial and four groups of posterior setae; palm distinctly oblique with double row of four inner and five outer spiniform setae of different size; palm groove (depression) feebly developed, palmar corner ( Fig. 7 g ) with three strong palmar spiniform setae, four supporting bifurcate setae on inner surface; dactylus with single seta along anterior margin and few short setae along inner margin.

Pereopod III ( Fig. 9 a ): coxal plate oval or sub-rectangular, with four apical and numerous facial setae, width/depth ratio is 0.5/1; basis about 4.7X as long as wide, with long anterior and posterior simple setae; merus about 0.67X of basis, about 1.52X of carpus and about 1.13X of propodus in length; carpus about 0.74X of propodus in length; dactylus ( Fig. 9 b ) about 0.37X of propodus, with single plumose seta on outer margin and single additional spine accompanying with single seta along ventral margin.

Pereopod IV ( Fig. 9 c ): subequal to PIII in length; coxal plate expanded and broadly convex distally, posterior margin with shallow excavation, distal margin with seven apical short setae and numerous facial setae, width/depth ratio is 0.86/1; basis about 5.0X as long as wide, with long anterior and posterior simple setae; merus about 0.64X of basis, about 1.36X of carpus and about 1.04X of propodus in length; carpus about 0.77X of propodus in length; dactylus ( Fig. 9 d ) about 0.42X of propodus, with single plumose seta on outer margin and single additional spine accompanying with single seta along ventral margin.

Pereopods V, VI, VII with length ratio 1/1.17/1.04.

Pereopod V ( Fig. 9 e ): coxal plate large, bilobate, with distinct anterior and posterior lobes; posterior and anterior lobes with single marginal simple seta each, with numerous facial setae; basis about 1.48X as long as wide, with numerous facial setae, posterior margin slightly convex, armed with 11 shallow serrations, with distinct distal corner, anterior margin with seven split-tipped robust and four distal setae; merus about 0.63X of basis, 0.91X of carpus and subequal of propodus in length; dactylus ( Fig. 9 f ) approximately 0.40X of propodus, with single plumose seta on outer margin and single additional spine accompanying with single seta along ventral margin.

Pereopod VI ( Fig. 9 g ): coxal plate bilobate, with distinct posterior and vestigial anterior lobes; anterior lobe without setae, posterior lobe with single margin seta, each with numerous facial setae; basis about 1.49X as long as wide, with numerous facial setae, posterior margin convex, armed with nine shallow serrations, anterior margin with seven tipped robust and three distal setae; merus about 0.66X of basis, 0.92X of carpus and 0.94X of propodus in length; dactylus ( Fig. 9 h ) approximately 0.38X of propodus, with single plumose seta on outer margin and an additional spine accompanying with single seta along ventral margin.

Pereopod VII ( Fig. 9 i ): coxal plate small, semi-lunar, with single posterior seta; basis about 1.56X as long as wide, with numerous facial setae, posterior margin convex, armed with eight serrated setae, with distal corner; anterior margin with seven split-tipped robust and three distal setae; merus about 0.66X of basis, about 1.28X of carpus and about 1.10X of propodus in length; dactylus ( Fig. 9 j ) approximately 0.40X of propodus in length, with single plumose seta on outer margin and an additional spine accompanying with single seta along ventral margin.

Gills, brood plates ( Fig. 9 ): coxal gills on somites II–VI, somites V–VIII with lanceolate sternal gill on each. Coxal gills of pereopods II–VI ovoid, gills/bases ratios are 0.73/1, 0.64/1, 0.67/1, 0.55/1 and 0.43/1, respectively.

Pleopods ( Fig. 10 g ): pleopods I–II with peduncles bearing two coupling hooks in retinacula ( Fig. 10 h ), without lateral setae; outer and inner rami with seven and eight segments, respectively; basal segments of outer ramus with single clothes-pin seta. Pleopod III peduncle with two coupling hooks in retinacula, without setae; outer and inner rami with six and seven segments, respectively; basal segment of outer ramus with single clothes-pin seta.

Epimera. Epimeral plate I ( Fig. 10 a ) weakly produced distally, almost straight, pointed, ventral margin without spines, posterior margin convex, with single seta. Epimeral plate II ( Fig. 10 b ) distally produced and sharply pointed, ventral margin armed with three spines, posterior margin oblique, with single seta. Epimeral plate III ( Fig. 10 c ) subtrapezoidal, blunted distally, ventral margin armed with two spines, posterior margin slightly oblique, with singleseta.

Urosomites fused partially: Urosomite I completely free, urosomites II and III fused, with distinct suture ( Fig. 10 d ).

Uropod I ( Fig. 10 i ): peduncle about 3.5X as long as wide, with dorsoexternal row of four short spines, 1 subdistal short spine and single dorsointernal spine; exopodite about 0.9X of endopodite in length; endopodite not paddle-like, with four dorsal and five apical spines; exopodite with five short dorsal and five apical spines.

Uropod II ( Fig. 10 j ): peduncle about 2.1X as long as wide, subequal of endopodite in length, with two long dorsoexternal spines; exopodite about 0.88X of endopodite in length, with three dorsal and five apical robust spines; endopodite with four dorsal and five apical robust spines.

Uropod III ( Fig. 10 k ): uniramous, peduncle cone-shaped, about 1.2X as long as wide, with rudimentary terminal “knob”, single simple seta on lateral margin and single spine on apical margin; peduncle about 1.1X of ramus in length; inner margin of ramus without spines, outer margin of ramus armed of single group of spines with two spines, apical margin armed with three spines.

Telson ( Fig. 10 e, f ): slightly narrowing distally, elongate, 0.75X as long as broad, slightly shorter as uropod III; apical margin cleft about 0.55X of total length; with five–six apical spines and two additional submarginal plumose setae on each lobe.

COLORATION. The body and appendages unpigmented, without well-developed pigmented eyes.

GENBANK ACCESSION NUMBERS. OQ534007, OQ534008.

TAXONOMIC REMARKS. The species can be most easily separated from D. waschuschtii by the following features: 1) apical margin cleft of telson is more than half of its total length ( Fig. 10 e, f ) vs. apical margin cleft of telson is clearly less than half of its total length [ Behning, 1940: fig. 17o]; 2) ramus and peduncle of uropod III approximately equal in length ( Fig. 10 k ) vs. ramus is significantly smaller than peduncle in length [ Behning, 1940: fig. 17n]; 3) rami of uropod III with group of lateral spines ( Fig. 10 k ) vs. rami of uropod III without lateral spines [ Behning, 1940: fig. 17n].

The species can be most easily separated from Diasynurella kiwi Marin et Palatov sp.n., by the following features: urosomites II–III completely fused ( Fig. 11 c ) vs. all urosomites completely free ( Fig. 11 a ); 2) uropod III is subequal to telson in length ( Fig. 11 c ) vs. uropod III is much longer than telson ( Fig. 11 a ); 3) inner plate of maxilla I with two plumose marginal setae ( Fig. 8 g ) vs. inner plate of maxilla I with four plumose marginal setae ( Fig. 3 g ).

For the differences from D. cavatica Palatov et Marin sp.n. and D. khalabensis Palatov et Marin sp.n. see below.

DISTRIBUTION AND ECOLOGY. The species is known only from single spring located in the Samur forest, Dagestan (northwestern Hyrcania). It is possible that the species inhabit other nearby springs and groudwaters, however, like other species the genus, it is extremely difficult to detect due to its very small size and habitat in the bottom sediment.

Figures

Fig. 6. Diasynurella dzhamirzoevi Palatov et Marin sp.n., Russia, Dagestan, Magaramkent district, Samur forest: general view of freshly fixed specimens. The arrows indicate eggs. Рис. 6. Diasynurella dzhamirzoevi Palatov et Marin sp.n., РоссиЯ, Дагестан, Магарамкентский район, Самурский лес: обЩий вид свежефиксированных обраЗцов. Стрелки укаЗывают на Яйцо.

Fig. 7. Diasynurella dzhamirzoevi Palatov et Marin sp.n., Russia, Dagestan, Magaramkent district, Samur forest: a — antenna I; b — accessory flagellum of antenna I; c — antenna II; d — gnathopod I; e — distoventral palmar margin of chela of GnI; f — gnathopod II; g — distoventral palmar margin of chela of GnII. Рис. 7. Diasynurella dzhamirzoevi Palatov et Marin sp.n., РоссиЯ, Дагестан, Магарамкентский район, Самурский лес: а — антенна I; b — вспомогательный жгутик антенны I; c — антенна II; d — гнатопода I; е — дистовентральный край клеШни GnI; f — гнатопода II; g — дистовентральный край клеШни GnII.

Fig. 8. Diasynurella dzhamirzoevi Palatov et Marin sp.n., Russia, Dagestan, Magaramkent district, Samur forest: a — labrum (upper lip); b — labium (lower lip); c — left mandible; d — same, incisor process and pars incisiva; e — right mandible; f — same, incisor process and pars incisiva; g — maxilla I; h — maxilla II; i — maxilliped. Рис. 8. Diasynurella dzhamirzoevi Palatov et Marin sp.n., РоссиЯ, Дагестан, Магарамкентский район, Самурский лес: a — верхнЯЯгуба; b — нижнЯЯ губа; c — леваЯ мандибула; d — то же самое, реЗцовый отросток и pars incisiva; e — праваЯ мандибула; f — то же самое, реЗцовый отросток и pars incisiva; g — максилла I; h — максилла II; i — максиллипед.

Fig. 9. Diasynurella dzhamirzoevi Palatov et Marin sp.n., Russia, Dagestan, Magaramkent district, Samur forest: a — pereopod III; b — dactylus of PIII; c — pereopod IV; d — dactylus of PIV; e — pereopod V; f — dactylus of PV; g — pereopod VI; h — dactylus of PVI; i — pereopod VII; j — dactylus of PVII. Рис. 9. Diasynurella dzhamirzoevi Palatov et Marin sp.n., РоссиЯ, Дагестан, Магарамкентский район, Самурский лес: a — переопода III; b — дактилус PIII; c — переопода IV; d — дактилус PIV; e — переопода V; f — дактилус PV; g — переопода VI; h — дактилус PVI; I — переопода VII; j — дактилус PVII.

Fig. 10. Diasynurella dzhamirzoevi Palatov et Marin sp.n., Russia, Dagestan, Magaramkent district, Samur forest: a — epimeral plate I; b — epimeral plate II; c — epimeral plate III; d — urosomal segments, lateral view; e, f — telson; g — pleopod III; h — hooks of retinacula of pleopod II; i — uropod I; j — uropod II; k — uropod III. Рис. 10. Diasynurella dzhamirzoevi Palatov et Marin sp.n., РоссиЯ, Дагестан, Магарамкентский район, Самурский лес: a — ЭпимеральнаЯ пластинка I; b — ЭпимеральнаЯ пластинка II; c — ЭпимеральнаЯ пластинка III; d — уросомальные сегменты, вид сбоку; e, f — тельсон; g — плеопода III; h — крючки ретинакулы плеоподы II; i — уропода I; j — уропода II; k — уропода III.

Fig. 11. Diasynurella kiwi Marin et Palatov sp.n. (a, b, h) and D. dzhamirzoevi Palatov et Marin sp.n. (c–g): a, c — urosomal segments, lateral view; b, d — head; e — gnathopod I; f — chela of gnathopod I; g, h — dactyli of ambulatory pereiopods (legs). Рис. 11. Diasynurella kiwi Marin et Palatov sp.n. (a, b, h) и D. dzhamirzoevi Palatov et Marin sp.n. (c–g): a, c — уросомальные сегменты, вид сбоку; b, d — голова; e — гнатопод I; f — клеШнЯ гнатоподы I; g, h — дактилусы амбулаторных переопод (ног).

Fig. 3. Diasynurella kiwi Marin et Palatov sp.n., Russia, Rostov Oblast’, Rostov-on-Don: a — labrum (upper lip); b — labium (lower lip); c — left mandible; d — same, incisor process and pars incisiva; e — right mandible; f — same, incisor process and pars incisiva; g — maxilla I; h — maxilla II; i — maxilliped. Рис. 3. Diasynurella kiwi Marin et Palatov sp.n., РоссиЯ, РостовскаЯ область, Ростов-на-Дону: a — верхнЯЯ губа; b — нижнЯЯ губа; c — леваЯ мандибула; d — то же самое, реЗцовый отросток и pars incisiva; e — праваЯ мандибула; f — то же самое, реЗцовый отросток и pars incisiva; g — максилла I; h — максилла II; i — максиллипед.